Gas-phase reactors, such as chemical vapor deposition (CVD), plasma-enhanced CVD (PECVD), atomic layer deposition (ALD), and the like can be used for a variety of applications, including depositing and etching materials on a substrate surface. For example, gas-phase reactors can be used to deposit and/or etch layers on a substrate to form semiconductor devices, flat panel display devices, photovoltaic devices, microelectromechanical systems (MEMS), and the like.
A typical gas-phase reactor system includes a reactor including a reaction chamber, one or more precursor gas sources fluidly coupled to the reaction chamber, one or more carrier or purge gas sources fluidly coupled to the reaction chamber, a gas distribution system to deliver gases (e.g., the precursor gas(es) and/or carrier or purge gas(es)) to a surface of a substrate, and an exhaust source fluidly coupled to the reaction chamber.
Many gas distribution systems include a showerhead assembly for distributing gas(es) to a surface of the substrate. The showerhead assembly is typically located above the substrate and is designed to provide laminar flow to the substrate surface. The showerhead assembly is generally designed, in connection with a reaction chamber, to provide desired residence times for gas-phase reactants.
During substrate processing, purge gases are often used to facilitate removal of one or more reactants and/or products from a reaction chamber. For example, during a typical ALD process, a first reactant (also referred to herein as a precursor) is introduced to the reaction chamber and allowed to react with a surface of a substrate for a first residence time, and the first reactant is evacuated from the reaction chamber using the exhaust system and a purge gas. A second reactant is then introduced to the reaction chamber to react with a surface of the substrate for a second residence time, which may be the same as or different from the first residence time. The second reactant is then evacuated from the reaction chamber using the exhaust system and a purge gas. These steps can be repeated until a desired amount of material is deposited onto a substrate surface.
During the purge steps, it may be desirable to allow considerably more gas—relative to a reactant—to flow through a reaction chamber. Unfortunately, ALD and other gas-phase reactors and systems are generally designed to restrict gas flow to optimize reactant flow rates and residence times to obtain desired film deposition rates and uniformity. As a result, the time required to sufficiently purge a reactant or other gas from a reaction chamber is undesirably long. Consequently substrate throughput can be undesirably slow and costs associated with processing the substrates can be undesirably high. Therefore, improved gas-phase methods and apparatus that allow rapid purging and desired reactant flow rates are desired.